[PATCH bpf-next v6 2/2] bpf: allow bpf_current_task_under_cgroup() with BPF_CGROUP_*

Matteo Croce
2024-08-19T16:28:42Z

The helper bpf_current_task_under_cgroup() currently is only allowed for
tracing programs, allow its usage also in the BPF_CGROUP_* program types.

Move the code from kernel/trace/bpf_trace.c to kernel/bpf/helpers.c,
so it compiles also without CONFIG_BPF_EVENTS.

This will be used in systemd-networkd to monitor the sysctl writes,
and filter it's own writes from others:
https://github.com/systemd/systemd/pull/32212

Signed-off-by: Matteo Croce <teknoraver@meta.com>
---
include/linux/bpf.h | 1 +
kernel/bpf/cgroup.c | 2 ++
kernel/bpf/helpers.c | 23 +++++++++++++++++++++++
kernel/trace/bpf_trace.c | 27 ++-------------------------
4 files changed, 28 insertions(+), 25 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index b9425e410bcb..f0192c173ed8 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -3206,6 +3206,7 @@ extern const struct bpf_func_proto bpf_sock_hash_update_proto;
extern const struct bpf_func_proto bpf_get_current_cgroup_id_proto;
extern const struct bpf_func_proto bpf_get_current_ancestor_cgroup_id_proto;
extern const struct bpf_func_proto bpf_get_cgroup_classid_curr_proto;
+extern const struct bpf_func_proto bpf_current_task_under_cgroup_proto;
extern const struct bpf_func_proto bpf_msg_redirect_hash_proto;
extern const struct bpf_func_proto bpf_msg_redirect_map_proto;
extern const struct bpf_func_proto bpf_sk_redirect_hash_proto;
diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
index 8ba73042a239..e7113d700b87 100644
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -2581,6 +2581,8 @@ cgroup_current_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
case BPF_FUNC_get_cgroup_classid:
return &bpf_get_cgroup_classid_curr_proto;
#endif
+ case BPF_FUNC_current_task_under_cgroup:
+ return &bpf_current_task_under_cgroup_proto;
default:
return NULL;
}
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 26b9649ab4ce..12e3aa40b180 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -2458,6 +2458,29 @@ __bpf_kfunc long bpf_task_under_cgroup(struct task_struct *task,
return ret;
}

+BPF_CALL_2(bpf_current_task_under_cgroup, struct bpf_map *, map, u32, idx)
+{
+ struct bpf_array *array = container_of(map, struct bpf_array, map);
+ struct cgroup *cgrp;
+
+ if (unlikely(idx >= array->map.max_entries))
+ return -E2BIG;
+
+ cgrp = READ_ONCE(array->ptrs[idx]);
+ if (unlikely(!cgrp))
+ return -EAGAIN;
+
+ return task_under_cgroup_hierarchy(current, cgrp);
+}
+
+const struct bpf_func_proto bpf_current_task_under_cgroup_proto = {
+ .func = bpf_current_task_under_cgroup,
+ .gpl_only = false,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_CONST_MAP_PTR,
+ .arg2_type = ARG_ANYTHING,
+};
+
/**
* bpf_task_get_cgroup1 - Acquires the associated cgroup of a task within a
* specific cgroup1 hierarchy. The cgroup1 hierarchy is identified by its
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index d557bb11e0ff..b69a39316c0c 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -797,29 +797,6 @@ const struct bpf_func_proto bpf_task_pt_regs_proto = {
.ret_btf_id = &bpf_task_pt_regs_ids[0],
};

-BPF_CALL_2(bpf_current_task_under_cgroup, struct bpf_map *, map, u32, idx)
-{
- struct bpf_array *array = container_of(map, struct bpf_array, map);
- struct cgroup *cgrp;
-
- if (unlikely(idx >= array->map.max_entries))
- return -E2BIG;
-
- cgrp = READ_ONCE(array->ptrs[idx]);
- if (unlikely(!cgrp))
- return -EAGAIN;
-
- return task_under_cgroup_hierarchy(current, cgrp);
-}
-
-static const struct bpf_func_proto bpf_current_task_under_cgroup_proto = {
- .func = bpf_current_task_under_cgroup,
- .gpl_only = false,
- .ret_type = RET_INTEGER,
- .arg1_type = ARG_CONST_MAP_PTR,
- .arg2_type = ARG_ANYTHING,
-};
-
struct send_signal_irq_work {
struct irq_work irq_work;
struct task_struct *task;
@@ -1480,8 +1457,6 @@ bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
return &bpf_get_numa_node_id_proto;
case BPF_FUNC_perf_event_read:
return &bpf_perf_event_read_proto;
- case BPF_FUNC_current_task_under_cgroup:
- return &bpf_current_task_under_cgroup_proto;
case BPF_FUNC_get_prandom_u32:
return &bpf_get_prandom_u32_proto;
case BPF_FUNC_probe_write_user:
@@ -1510,6 +1485,8 @@ bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
return &bpf_cgrp_storage_get_proto;
case BPF_FUNC_cgrp_storage_delete:
return &bpf_cgrp_storage_delete_proto;
+ case BPF_FUNC_current_task_under_cgroup:
+ return &bpf_current_task_under_cgroup_proto;
#endif
case BPF_FUNC_send_signal:
return &bpf_send_signal_proto;
--
2.46.0